1. Field of the Disclosure
The disclosure generally relates to a lens. More particularly, the disclosure relates to a zoom lens.
2. Description of Related Art
Along with development of optoelectronic technology, image apparatuses such as projectors, digital video cameras (DVC), digital cameras (DC) and the like have been extensively used in our daily life. The zoom lens is one of the core devices of the image apparatuses. By adjusting the zoom lens, an image may be clearly focused on a screen or a charge coupled device (CCD) for forming the image. Thus, the imaging quality and the optical quality of the zoom lens are closely related. With drastic competitions in the market, all manufacturers focus on improving the optical quality of the zoom lens and reducing weight, volume and manufacturing cost thereof, so as to improve the competition of the image apparatus at an advantageous position.
In the conventional technology, in order to achieve advantages of better imaging quality and compactness, in general, the zoom lens is configured as composed of two lens groups, wherein the first lens group located near the object side has a negative refractive power, and the second lens group located near the image side has a positive refractive power, namely, the first lens group is used for diverging light beams while the second lens group is used for converging light beams. In the first lens group, the surface facing the object side may be exposed outside the zoom lens or outside a cover body of an image apparatus, thus if the surface facing the object side is a convex surface or a concave surface, resulting that dust may easily accumulate on the surface and the brightness and clearness of the image formed by the image apparatus may be affected. In addition, if the surface facing the object side is a convex surface whose spherical center is at the image side, the light beam transmitted to the surface is easily be reflected back to the image processing unit which is located at the image side, and the light beam which is reflected back to the image processing unit is easily to be projected onto the screen and generates cross-talk which affects the imaging quality.
The information disclosed in the “Description of Related Art” section is only for enhancement of understanding of the background of the described technology, and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art. Further, the information disclosed in the “Description of Related Art” section does not mean that one or more problems to be resolved by one or more embodiments of the invention was acknowledged by a person of ordinary skill in the art.